code/mandelbrot/mandelbrot.c

#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>


#include "../libpng/img.h"
#include "config.h"

typedef struct mandel_field_t {
	int h, w;
	int * arr;
	pthread_mutex_t mut;
} mandel_field_t;

typedef struct mandel_t {
	int x, y;
	int bail_out;
	int max_iter;
	mandel_field_t field;
} mandel_t;

typedef struct inner {
	pthread_mutex_t mut;
} inner;

typedef struct buffer {
	sem_t empty;
	sem_t full;
	pthread_mutex_t mut;
	int pos;
	mandel_t ** pix;
	inner * in;
} buffer;



double map(int value, int min, int max, int map_min, int map_max)
{
	double R = (double) (map_max - map_min) / (double) (max - min);
	double y = map_min + (value * R) + R;
	return y;
}


int mandelbrot_pix(double x, double y, int bail_out, int max_iter)
{
	int k;
	double real, imaginary, x2, y2;

	x2 = x;
	y2 = y;

	// iterate a^2 - b^2 + 2ab
	for (k = 0; k < max_iter; k++) {
		// a^2 - b^2
		real = x * x - y * y;
		// 2ab
		imaginary = 2 * x * y;

		// x = real + c
		x = real + x2;
		// y = imaginary + c
		y = imaginary +y2;

		if ((x * x + y * y) > bail_out) {
			return k;
		}
	}
	return max_iter;
}

void init_buffer(buffer * buf)
{
	sem_init(&buf->empty, 0, 0);
	sem_init(&buf->full, 0, BUFFER_SIZE);
	buf->in = malloc(sizeof(inner));
	buf->pos = 0;
	buf->pix = malloc(sizeof(mandel_t) * BUFFER_SIZE);

	for (int i = 0; i < BUFFER_SIZE; i++) {
		buf->pix[i] = NULL;
	}
}

void mandel_field_setXY(mandel_field_t m, int x, int y, int value){
	pthread_mutex_lock(&m.mut);
	m.arr[x * m.h + y] = value;
	pthread_mutex_unlock(&m.mut);
}

void * mandel_consumer(void *buff)
{
	buffer * buf = (buffer *) buff;
	mandel_t * pix;
	int count = 0;
	double xPrime, yPrime;

	while(1) {

		int tw = sem_trywait(&buf->empty);
		if (tw == 0) {
			pthread_mutex_lock(&buf->mut);
			
			buf->pos = buf->pos - 1;
			pix = buf->pix[buf->pos];
			count ++;
			sem_post(&buf->full);
			

			xPrime = map(pix->x, 0, pix->field.w, -2, 2);
			yPrime = map(pix->y, 0, pix->field.h, -2, 2);

			int k = mandelbrot_pix(xPrime, yPrime, pix->bail_out, pix->max_iter);
			mandel_field_setXY(pix->field, pix->x, pix->y, k);
			pthread_mutex_unlock(&buf->mut);
		} else {
			int rc = pthread_mutex_trylock(&buf->in->mut);
			if (rc == 0){
				printf("\ngot lock");
				pthread_mutex_unlock(&buf->in->mut);
				pthread_exit(NULL);
			}
		}
	}
}

void mandelbrot(int * field, int w, int h, int bail_out, int max_iter,
		int thread_count)
{
	double xPrime, yPrime;
	int x, y, k;
	
	buffer *buf;
	buf = malloc(sizeof(buffer));
	init_buffer(buf);

	pthread_t t[thread_count];
	pthread_attr_t attr;

	pthread_attr_init(&attr);

	pthread_mutex_lock(&buf->in->mut);
	for (int i=0;i<thread_count;i++) {
		pthread_create(&t[i], &attr, mandel_consumer, buf);
	}

	for (int i=0; i<w;i++) {	
		for (int j=0; j<h;j++) {	
			sem_wait(&buf->full);
			pthread_mutex_lock(&buf->mut);

			
			buf->pix[buf->pos] = malloc(sizeof(mandel_t));
			buf->pix[buf->pos]->x = i;
			buf->pix[buf->pos]->y = j;
			buf->pix[buf->pos]->bail_out = bail_out;
			buf->pix[buf->pos]->max_iter = max_iter;
			buf->pix[buf->pos]->field.arr = field;
			buf->pix[buf->pos]->field.h = h;
			buf->pix[buf->pos]->field.w = w;
			buf->pos += 1;

			sem_post(&buf->empty);
			pthread_mutex_unlock(&buf->mut);
		}
	}
	pthread_mutex_unlock(&buf->in->mut);
	printf("Finished filling the buffer");

	for (int i=0;i<thread_count;i++) {
		pthread_join(t[i], NULL);
	}

	free(buf->in);
	free(buf->pix);
	free(buf);
}

int main(int argc, char **argv)
{

	int * pix_field;

	pix_field = malloc(WIDTH * HEIGHT * sizeof(int));

	printf
	    ("WIDTH: %d\nHEIGHT %d\nBAIL OUT %d\nMAX ITER %d\nTHREAD COUNT %d",
	     WIDTH, HEIGHT, BAIL_OUT, MAX_ITER, THREAD_COUNT);


	mandelbrot(pix_field, WIDTH, HEIGHT, BAIL_OUT, MAX_ITER,
		   THREAD_COUNT);

	pix_row rows[WIDTH];
	pix p;

	char filename[30];
	image img;
	p.r = 200;
	p.g = 200;
	p.b = 200;

	for (int i = 0; i < WIDTH; i++) {
		rows[i].p = malloc(HEIGHT * sizeof(pix));
		for (int j = 0; j < HEIGHT; j++) {
			p.r =
			    map(pix_field[i * HEIGHT + j], 0, MAX_ITER, 0,
				255);
			p.g =
			    map(pix_field[i * HEIGHT + j], 0, MAX_ITER, 0,
				255);
			p.b =
			    map(pix_field[i * HEIGHT + j], 0, MAX_ITER, 0,
				255);
			rows[i].p[j] = p;
		}
	}
	sprintf(filename, "mandel.png");
	img = initialize_png("mandelbrot", filename, WIDTH, HEIGHT);
	write_image(&img, rows);
	finish_image(&img);
	for (int i = 0; i < WIDTH; i++) {

		free(rows[i].p);
	}

	free(pix_field);

	return (0);
}